Semiconductor device assembly with vapor chamber

ABSTRACT

Semiconductor device assemblies having stacked semiconductor dies and thermal transfer devices that include vapor chambers are disclosed herein. In one embodiment, a semiconductor device assembly includes a first semiconductor die, a second semiconductor die on a base region of the first die, and a thermal transfer device attached to a peripheral region of the first die and extending over the second die. The thermal transfer device includes a conductive structure having an internal cavity and a working fluid at least partially filling the cavity. The conductive structure further includes first and second fluid conversion regions adjacent the cavity. The first fluid conversion region transfers heat from at least the peripheral region of the first die to a volume of the working fluid to vaporize the volume in the cavity, and the second fluid conversion region condenses the volume of the working fluid in the cavity after it has been vaporized.

RELATED APPLICATION(S)

This application is a divisional of U.S. patent application Ser. No.14/720,015, filed May 22, 2015, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The disclosed embodiments relate to semiconductor device assemblies, andin particular to semiconductor device assemblies having thermal transferdevices that include vapor chambers.

BACKGROUND

Packaged semiconductor dies, including memory chips, microprocessorchips, and imager chips, typically include a semiconductor die mountedon a substrate and encased in a plastic protective covering. The dieincludes functional features, such as memory cells, processor circuits,and imager devices, as well as bond pads electrically connected to thefunctional features. The bond pads can be electrically connected toterminals outside the protective covering to allow the die to beconnected to higher level circuitry.

Semiconductor manufacturers continually reduce the size of die packagesto fit within the space constraints of electronic devices, while alsoincreasing the functional capacity of each package to meet operatingparameters. One approach for increasing the processing power of asemiconductor package without substantially increasing the surface areacovered by the package (i.e., the package's “footprint”) is tovertically stack multiple semiconductor dies on top of one another in asingle package. The dies in such vertically-stacked packages can beinterconnected by electrically coupling the bond pads of the individualdies with the bond pads of adjacent dies using through-silicon vias(TSVs). In vertically stacked packages, the heat generated is difficultto dissipate, which increases the operating temperatures of theindividual dies, the junctions therebetween, and the package as a whole.This can cause the stacked dies to reach temperatures above theirmaximum operating temperatures (T_(max)) in many types of devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a semiconductor device assemblyconfigured in accordance with an embodiment of the present technology.

FIG. 2 is a cross-sectional view of the semiconductor device assembly ofFIG. 1 after it has been heated to an elevated temperature in accordancewith an embodiment of the present technology.

FIGS. 3-5 are cross-sectional views of semiconductor device assembliesconfigured in accordance with other embodiments of the presenttechnology

FIG. 6 is a schematic view of a system that includes a semiconductordevice in accordance with embodiments of the present technology.

DETAILED DESCRIPTION

Specific details of several embodiments of semiconductor deviceassemblies having thermal transfer devices that include vapor chambersare described below. The term “semiconductor device” generally refers toa solid-state device that includes semiconductor material. Asemiconductor device can include, for example, a semiconductorsubstrate, wafer, or die that is singulated from a wafer or substrate.Throughout the disclosure, semiconductor devices are generally describedin the context of semiconductor dies; however, semiconductor devices arenot limited to semiconductor dies.

The term “semiconductor device package” can refer to an arrangement withone or more semiconductor devices incorporated into a common package. Asemiconductor package can include a housing or casing that partially orcompletely encapsulates at least one semiconductor device. Asemiconductor device package can also include an interposer substratethat carries one or more semiconductor devices and is attached to orotherwise incorporated into the casing. The term “semiconductor deviceassembly” can refer to an assembly of one or more semiconductor devices,semiconductor device packages, and/or substrates (e.g., interposer,support, or other suitable substrates). As used herein, the terms“vertical,” “lateral,” “upper,” and “lower” can refer to relativedirections or positions of features in the semiconductor device in viewof the orientation shown in the Figures. For example, “upper” or“uppermost” can refer to a feature positioned closer to the top of apage than another feature. These terms, however, should be construedbroadly to include semiconductor devices having other orientations, suchas inverted or inclined orientations where top/bottom, over/under,above/below, up/down, and left/right can be interchanged depending onthe orientation.

FIG. 1 is a cross-sectional view of a semiconductor device assembly 100(“assembly 100”) configured in accordance with an embodiment of thepresent technology. As shown, the assembly 100 includes a packagesupport substrate 102 (e.g., an interposer), a first semiconductor die104 on the substrate 102, a plurality of second semiconductor dies 106mounted to the first die 104, and a thermal transfer device (TTD) 108over the first and second dies 104 and 106. The TTD 108 includes aconductive structure, or envelope 110, having an upper region 112extending over the second dies 106, and an outer region 114 attached tothe package support substrate 102 with a first adhesive 117. The TTD 108forms an enclosure 116 with the first die 104 that contains theplurality of second dies 106.

The first die 104 includes a base region 118 and a peripheral region 120(known to those skilled in the art as a “porch” or “shelf”) adjacent thebase region 118. The second dies 106 are arranged in a stack 124 (“diestack 124”) on the base region 118 and attached to the upper region 112of the TTD 108 with a second adhesive 126, which can be the sameadhesive as the first adhesive 117 or a different adhesive. Suitableadhesives can include, for example, a thermal interface material (“TIM”)or other adhesive containing, e.g., silicone-based greases, gels, oradhesives that are doped with conductive materials (e.g., carbonnano-tubes, solder materials, diamond-like carbon (DLC), etc.), as wellas phase-change materials.

The first and second dies 104 and 106 can include various types ofsemiconductor components and functional features, such as dynamicrandom-access memory (DRAM), static random-access memory (SRAM), flashmemory, other forms of integrated circuit memory, processing circuits,imaging components, and/or other semiconductor features. In variousembodiments, for example, the assembly 100 can be configured as a hybridmemory cube (HMC) in which the stacked second dies 106 are DRAM dies orother memory dies that provide data storage and the first die 104 is ahigh-speed logic die that provides memory control (e.g., DRAM control)within the HMC. In other embodiments, the first and second dies 104 and106 may include other semiconductor components and/or the semiconductorcomponents of the individual second dies 106 in the die stack 124 maydiffer. In the embodiment illustrated in FIG. 1, the first die 104includes an integrated circuit 128 that extends at least partially intothe peripheral region 120. In one embodiment, the portion of theintegrated circuit 128 that extends into the peripheral region 120 caninclude one or more circuit components that produce relatively largeamounts of heat during operation, such as serial/deserializer (SERDES)circuits. In a related embodiment, circuit components that producerelatively smaller amounts of heat during operation can be located awayfrom the peripheral region and/or directly beneath the die stack.

The die stack 124 can be electrically coupled to the package supportsubstrate 102 and to one another by a plurality of electricallyconductive elements 130 (e.g., copper pillars, solder bumps, and/orother conductive features). Each of the first and second dies 104 and106 can include a plurality of through-silicon vias (TSVs) 131 that arecoupled on opposite sides to the conductive elements 130. In addition toelectrical communication, the conductive elements 130 and the TSVs 131transfer heat away from the die stack 124 and toward the TTD 108. Insome embodiments, the assembly 100 can also include a plurality ofthermally conductive elements or “dummy elements” (not shown) positionedinterstitially between the first and second dies 104 and 106 to furtherfacilitate heat transfer through the die stack 124. Such dummy elementscan be at least generally similar in structure and composition to theconductive elements 130 and/or the TSVs 131 except that they are notelectrically coupled to the other circuitry of the first and second dies104 and 106. In some embodiments, the assembly 100 can further includean underfill material (not shown) between each of the second dies 106and between the first die 104 and the bottom second die 106 to providemechanical support and electrical isolation between the conductiveelements 130.

In the embodiment illustrated in FIG. 1, the envelope 110 of the TTD 108includes a continuous conductive wall 132, an interior surface 134 alongthe wall 132 forming an internal cavity 136 (e.g., a vapor chamber), awicking feature 138 covering at least a portion of the interior surface134, and a working fluid 140 (e.g., a heat transfer fluid) partiallyfilling the cavity 136. The conductive wall 132 includes a first wallportion 144 a extending over the peripheral region 120 of the first die104 and projecting vertically alongside the die stack 124, a second wallportion 144 b extending over the upper second die 106 of the die stack124, and a third wall portion 144 c generally surrounding the exteriorside of the cavity 136. In some embodiments, the envelope 110 of the TTD108 can be formed from thermally conductive materials, such as copper,aluminum, ceramic materials, or other materials having suitably highthermal conductivities. In one embodiment, the envelope 110 is formedfrom extruded metal that is crimped or bent to define the shape of theenvelope. In another embodiment, the envelope 110 is formed fromconductive metal members joined together by brazing or other metaljoining processes. In these and other embodiments, the conductive wall132 of the envelope can be formed from a thin metal having a thicknessthat is less than or equal to 3 mm (e.g., 1 mm or less). In certainembodiments, the TTD 108 can include other structures and/or featuresattached to or integral formed in the conductive wall 132 for enhancedheat dissipation. For example, the TTD 108 can include an additionalheat sink (not shown), such as conductive fins or an additional outercasing, attached to the package support substrate 102.

The working fluid 140 can include, for example, alcohol (e.g.,methanol), ammonia, acetone, water, (e.g., distilled water), or othersuitable heat transfer fluids chosen according to the operatingtemperature of the assembly 100 and/or material(s) of the envelope 110.For example, in one embodiment water can be used as a working fluid in aconductive envelope formed from copper, and can provide evaporativecooling over a temperature range of, e.g., 20 to 150° C. The wickingfeature 138 can include, for example, a sintered powder (e.g., powderedcopper), a porous or mesoporous material, a mesh material (e.g., acopper mesh), or other suitable material for transporting the workingfluid 140 (e.g., via capillary forces) along the conductive wall 132 ofthe envelope 110 when the working fluid 140 is in a saturated or liquidphase. In some embodiments, the wicking feature 138 can include surfacefeatures, such as grooves (not shown), configured to facilitate fluidtransport.

In the embodiment illustrated in FIG. 1, the cavity 136 extends over theupper second die 106 and the peripheral region 120 of the first die 104,and surrounds the die stack 124. The cavity 136 can be filled with theworking fluid 140 through an opening 148 of a fluid inlet 142 extendingthrough the conductive wall 132 of the envelope 110. The fluid inlet 142can be capped with a plug 146 (e.g., a metal or plastic plug) that seals(e.g., hermetically seals) the cavity 136. In at least some embodiments,the plug 146 may be removable from the opening 148 so that the workingfluid 140 can be replenished through the inlet 142. In otherembodiments, the fluid inlet 142 can be permanently sealed. For example,in one embodiment the conductive wall 132 can include integral tabs 150(shown in phantom lines) adjacent the fluid inlet 142 and which can bebent (e.g., crimped) to close the opening 148 and substantially seal thefluid inlet 142.

In FIG. 1, the assembly 100 is at a first temperature level T₁ (e.g.,room temperature) below operating temperature, and the working fluid 140is substantially in a liquid-phase at the first temperature level T₁.FIG. 2 shows the assembly 100 after it has been heated from the firsttemperature level T₁ of FIG. 1 to a second temperature level T₂ greaterthan temperature level T₁ during operation. As shown in FIG. 2, the TTD108 includes a plurality of fluid conversion regions 260 (referred toindividually as a first evaporation region 260 a, a second evaporationregion 260 b, and a condensation region 260 c, respectively). The firstevaporation region 260 a includes the first wall portion 144 a, thesecond evaporation region 260 b includes the second wall portion 144 b,and the condensation region 260 c includes the third wall portion 144 c.The fluid conversion regions 260 can also include a portion of thewicking feature 138.

As the assembly 100 is heated to and/or operating at the secondtemperature T₂, the peripheral region 120 of the first die 104 transfersits heat into the first evaporation region 260 a through the first wallportion 144 a of the TTS 108, as shown by arrows F. The second dies 106,similarly, transfers their heat into the second evaporation region 260 bthrough the second wall portion 144 b, as shown by arrows H. The firstand second wall portions 144 a and 144 b, in turn, transfer heat intoliquid-phase, or saturated, volumes (not shown) of the working fluid 140(FIG. 1) located in or near the evaporation regions 260 a and 260 b. Thetransferred heat raises the temperature of the saturated working fluid140. Additionally, the working fluid 140 draws latent heat from theevaporation regions 260 a and 260 b as the saturated fluid approachesits vaporization temperature. This leads to further cooling of the firstand second dies 104 and 106 and, ultimately, to evaporation of thesaturated fluid in the cavity 136 into vapor phase. The vapor-phasefluid flows toward the condensation region 260 c due to thermaldiffusion and the difference in vapor pressure across the cavity 136caused by the local heating in the evaporation regions 260 a and 260 b.The vapor-phase fluid condenses in the condensation region 260 c due tothe relatively lower temperature of the third wall portion 144 c. As theworking fluid 140 condenses, it releases its latent heat into the thirdwall portion 144 c, and the wall portion 144 c, in turn, transfers thelatent heat to the external environment outside of the TTD 108. Thecondensed working fluid then returns to the evaporation regions 260 aand 260 b via the wicking feature 138 (e.g., via capillary action)and/or gravity, and evaporative cooling can continue as the condensedworking fluid 140 is re-heated and vaporized in the evaporation regions260 a and 260 b and, again, condensed in the condensation region 260 c.

Without being bound to theory, it is believed that TTDs configured inaccordance with the various embodiments of the present technology canprovide highly efficient heat transfer and reduce the overall operatingtemperatures of the assembly 100 or other semiconductor deviceassemblies by at least 5° C. compared to similar assemblies havingthermally conductive structures (e.g., solid-metal lid structures)formed without a vapor chamber. It is believed that in at least some ofthese embodiments, operating temperature can be reduced by 10° C. ormore. Additionally, another advantage of the TTD 108 and related thermaltransfer devices, is that they uniformly distribute heat across theassembly 100 due to the relatively large thermal diffusion rates of thevapor-phase fluid in the cavity 136. For example, a higher temperaturevapor will typically flow toward a region occupied by a lowertemperature vapor to achieve thermal equilibrium of the working fluid140. In the case of HMC devices, this can be particularly useful becausethe first die 104 is usually a logic die and the second dies 106 aregenerally memory dies, and logic dies typically operate at a much higherpower level than memory dies. Additionally, the integrated circuitcomponents (e.g., SERDES components) in the peripheral region 120generally have a higher power density than the integrated circuitcomponents in the base region 118 beneath the memory dies, which resultsin higher temperatures at the peripheral region 120 and highertemperature vapors produced in the evaporation regions 260 a and 260 b.By contrast, other assemblies having thermally conductive structuresformed with, e.g., solid materials (rather than hollow vapor chambers)do not achieve the same thermal equilibrium because solid materials havea low rate of thermal diffusion. As a result, the heat typicallyconcentrates in the conductive structure above the higher temperatureregions of these assemblies, such as above the peripheral region of alogic die.

FIG. 3 is a cross-sectional view of a semiconductor device assembly 300(“assembly 300”) having a TTD 308 configured in accordance with anotherembodiment of the present technology. Several features of the assembly300 are similar to those described above with respect to the assembly100. For example, the assembly can include the die stack 124 arranged onthe first die 104, and the TTD 308 can include a conductive structure310 having a conductive wall 332 and an internal cavity 336 partiallyfilled with a working fluid (not shown). In the embodiment illustratedin FIG. 3, however, the TTD 308 includes a generally solid conductivemember, or spacer 370, having a first side 372 attached to theperipheral region 120 of the first die 104 with a first adhesive 371 andalso attached to a peripheral region 375 of the package supportsubstrate 102 with a second adhesive 376 (e.g., a TIM). The spacer 370further includes a second side 373 opposite the first side 373 andattached to an outer region 314 of the conductive structure 310 with athird adhesive 379 (e.g., a TIM). In certain embodiments, the spacer 370can mechanically stiffen the conductive structure 310. For example, thespacer 370 can reduce the length of vertical wall portions 335 and 337along the interior and exterior sides, respectively, of the conductivewall 332. In some cases, the shorter vertical wall portions 335 and 337can be less prone to deform or collapse when mechanical forces areapplied to the conductive wall 332, such as when installing the TTD 308on package support substrate 102, or when installing the assembly 300 onan external support substrate (e.g., a printed circuit board; notshown). Further, the shape of the conductive wall 332 may be relativelyeasier to form compared to the shape of the conductive wall 132 of theTTD 108 of FIG. 1. In particular, the conductive wall 332 does not wraparound the lateral edge of the first die 104, but instead projects alonga straight path above the spacer 370. In cases where the conductive wall332 is formed from crimped or bent metal, this can reduce the number ofbends or folds needed to form the exterior shape of the TTD 308. In someembodiments, the spacer 370 can be formed from a thermally conductivematerial, such as copper, aluminum, nickel, or other material having asuitably high thermal conductivity. In other embodiments, the spacer 370can be formed from a semiconductor material, such as silicon. Forexample, in one embodiment, the spacer can be been cut or cleaved from asilicon wafer.

FIG. 4 is a cross-sectional view of a semiconductor device assembly 400(“assembly 400”) having a TTD 408 configured in accordance with anotherembodiment of the present technology. Several features of the assembly400 are similar to those described above with respect to the assemblies100 and 300 described above. For example, the TTD 408 can include aconductive structure 410 having a conductive wall 432 and an internalcavity 436 partially filled with a working fluid (not shown). In theembodiment illustrated in FIG. 4, however, the conductive wall 432defines a generally rectangular shape, and the TTD 408 does not extenddownwardly toward the first die 104. Instead, the TTD 408 includes aconductive member, or spacer 480, projecting vertically from theperipheral regions 120 and 375 of the first die 104 and the packagesupport substrate 102, respectively, and alongside the first die 104 andthe die stack 124. Similar to the spacer 370 of FIG. 3, the spacer 480can be formed from a variety of thermally conductive materials, such ascopper, aluminum, silicon, etc. In at least some embodiments, therectangular shape of the conductive wall 432 may be relatively easier tomanufacture (e.g., from crimped metal) than the “C”-shape of theconductive walls of the TTDs 108 and 308 of FIGS. 1 and 3. Theconductive wall 432 can, nevertheless, form a vapor chamber thatsubstantially increases heat transfer and heat distribution uniformityrelative to other device assemblies having thermal transfer deviceswithout vapor chambers.

FIG. 5 is a cross-sectional view of a semiconductor device assembly 500(“assembly 500”) having a TTD 508 configured in accordance with anotherembodiment of the present technology. The TTD 508 is generally similarto the TTD 408 of FIG. 4, but includes a generally solid conductivemember 580 that projects beyond the upper second die 106. The TTD 508also includes a thermal transfer structure 510 that lies within thefootprint of the die stack 124, and thus does not extend over theperipheral regions 120 and 375 of the first die 104 and the packagesupport substrate 102, respectively.

Any one of the stacked semiconductor device assemblies described abovewith reference to FIGS. 1-5 can be incorporated into any of a myriad oflarger and/or more complex systems, a representative example of which issystem 680 shown schematically in FIG. 6. The system 680 can include asemiconductor device assembly 600, a power source 682, a driver 684, aprocessor 686, and/or other subsystems or components 688. Thesemiconductor device assembly 600 can include features generally similarto those of the semiconductor device assemblies described above withreference to FIGS. 1-5, and can therefore include various features thatenhance heat dissipation. The resulting system 680 can perform any of awide variety of functions, such as memory storage, data processing,and/or other suitable functions. Accordingly, representative systems 680can include, without limitation, hand-held devices (e.g., mobile phones,tablets, digital readers, and digital audio players), computers,vehicles, appliances and other products. Components of the system 680may be housed in a single unit or distributed over multiple,interconnected units (e.g., through a communications network). Thecomponents of the system 480 can also include remote devices and any ofa wide variety of computer readable media.

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. Further, although many of the embodiments of thesemiconductor dies assemblies are described with respect to HMCs, inother embodiments the semiconductor die assemblies can be configured asother memory devices or other types of stacked die assemblies. Inaddition, certain aspects of the new technology described in the contextof particular embodiments may also be combined or eliminated in otherembodiments. Moreover, although advantages associated with certainembodiments of the new technology have been described in the context ofthose embodiments, other embodiments may also exhibit such advantagesand not all embodiments need necessarily exhibit such advantages to fallwithin the scope of the technology. Accordingly, the disclosure andassociated technology can encompass other embodiments not expresslyshown or described herein.

I/We claim:
 1. A method for manufacturing a semiconductor deviceassembly having a thermal transfer device that includes a conductivestructure having an internal cavity, a working fluid at least partiallyfilling the cavity, a first fluid conversion region adjacent the cavity,and a second fluid conversion region adjacent the cavity, wherein themethod comprises: positioning a first semiconductor die on a base regionof a second semiconductor die; and attaching the thermal transfer deviceat least to a peripheral region of the second semiconductor die adjacentto the base region and such that— at least a portion of the thermaltransfer device extends over the first semiconductor die, the firstfluid conversion region transfers heat from the peripheral region of thefirst semiconductor die to a volume of the working fluid to vaporize thevolume in the cavity, and the second fluid conversion region condensesthe volume of the working fluid in the cavity after it has beenvaporized.
 2. The method of claim 1 wherein the conductive structureincludes an outer region containing a first portion of the cavity and anupper region containing a second portion of the cavity, and whereinattaching the thermal transfer device includes attaching the outerregion to the peripheral region of the first semiconductor die, andattaching the upper region to the second semiconductor die.
 3. Themethod of claim 2 wherein the second semiconductor die includes aperimeter, wherein the peripheral region is adjacent to the perimeter,and wherein the base region is laterally inboard of the peripheralregion.
 4. The method of claim 2 wherein the outer region of theconductive structure entirely surrounds a perimeter of the firstsemiconductor die.
 5. The method of claim 1 wherein attaching thethermal transfer device includes coupling a first side of a solidconductive member to the peripheral region of the first semiconductordie and a second side of the conductive member opposite the first sideto a portion of the conductive structure.
 6. The method of claim 5wherein coupling the first and second portions of the conductive memberincludes attaching the first side to the peripheral region with a firstthermal interface material, and attaching the second side to the portionof the conductive member with a second thermal interface material. 7.The method of claim 5 wherein the conductive member comprises copper. 8.The method of claim 5 wherein the conductive member comprises a siliconspacer.
 9. The method of claim 1 attaching the thermal transfer deviceincludes forming an enclosure with the second semiconductor die thatencloses the first semiconductor die.
 10. The method of claim 1, furthercomprising attaching a package support substrate to the secondsemiconductor die and to a portion of the thermal transfer deviceperipheral to the second semiconductor die.
 11. The method of claim 10wherein attaching the package support substrate to the portion of thethermal transfer device includes attaching the package support substratedirectly to the portion of the thermal transfer device via an adhesivematerial.
 12. The method of claim 1, further comprising: attaching apackage support substrate to the second semiconductor die; attaching agenerally solid conductive member to the support substrate via a firstadhesive; and attaching the thermal transfer device to the conductivemember via a second adhesive.
 13. The method of claim 1 wherein thefirst semiconductor die comprises a memory die, and the secondsemiconductor die comprises a logic die.
 14. A method of operating asemiconductor device assembly having a first semiconductor die, a secondsemiconductor die at a base region of the first semiconductor die, and athermal transfer device extending over the second semiconductor die andattached to a peripheral region of the first semiconductor die adjacentthe base region, wherein the thermal transfer device includes aconductive structure having an internal cavity and a working fluid atleast partially filling the cavity, wherein the method comprises:transferring heat from at least the peripheral region of the firstsemiconductor die to a volume of the working fluid to vaporize thevolume in the cavity, and condensing the volume of the working fluid inthe cavity after it has been vaporized.
 15. The method of claim 14wherein the conductive structure includes a conductive wall defining thecavity and extending over the second semiconductor die, whereincondensing the volume of the working fluid includes condensing thevolume of working fluid via the conductive wall.
 16. The method of claim14 wherein the conductive structure includes a conductive wall definingthe cavity, wherein the conductive wall includes a first wall portionthat extends over the peripheral region of the first semiconductor die,and a second wall portion that extends over the second semiconductordie, and wherein: transferring heat from at least the peripheral regionof the first semiconductor die includes transferring heat to the volumeof the working fluid via the first wall portion; and condensing thevolume of the working fluid includes condensing the volume of workingfluid via the second wall portion.
 17. The method of claim 16 whereinthe conductive wall includes a third wall portion extending over thesecond die, and wherein transferring heat from at least the peripheralregion of the first semiconductor die further includes transferring heatvia the third wall portion.
 18. The method of claim 14 wherein theconductive structure includes a conductive wall defining the cavity andextending over peripheral region of the first semiconductor die, andwherein transferring heat from at least the peripheral region of thefirst semiconductor die includes transferring heat to the volume of theworking fluid through a portion of the conductive wall.
 19. The methodof claim 18 wherein the thermal transfer device further includes awicking feature over the portion of the conductive wall, and whereintransferring heat from at least the peripheral region of the firstsemiconductor die includes transferring heat via the wicking feature.20. The method of claim 18 wherein the thermal transfer device furtherincludes a generally solid conductive member coupling the thermallyconductive structure to the peripheral region of the first semiconductordie, and wherein transferring heat from at least the peripheral regionof the first semiconductor die includes transferring heat via theconductive member.